1. Technical Field
The present disclosure relates to an apparatus for power wireless transfer between two devices and simultaneous data transfer.
2. Description of the Related Art
Power wireless transfer between first and second devices is known in the state of the art, e.g., for recharging the battery of a mobile phone or of an electro-medical apparatus; the magnetic field generated by a resonant inductive coupling between the two devices is exploited to wirelessly transfer power.
The first device or source device comprises a resonant circuit of series type formed by a coil L1 having air as an insulator and a capacitor C1 connected in series to the coil and to a resistor R1.
The second device comprises a resonant circuit of parallel type with a coil L2 on a plastic or ceramic support which is arranged in parallel to a capacitor C2 and a resistor R2. Both the resonant circuits of the devices are tuned to resonate at the same resonant frequency fo and for which the relation
  fo  =      1          2      ·      π      ·                        L          ·          C                    is true, with L1*C1=C2*L2=L*C. The impedance of the circuit at the resonant frequency is minimal for the series circuit and maximum for the parallel circuit. The quality coefficient is defined for both circuits, considering the losses due to parasitic elements; with Q1 indicating the quality coefficient of the series circuit, the result is
      Q    ⁢                  ⁢    1    =                    2        ·        π        ·        fo        ·        L                    R        ⁢                                  ⁢        1              =                  1                  R          ⁢                                          ⁢          1                    ⁢                        L          C                    and with Q2 indicating the quality coefficient of the parallel circuit, the results is Q2=2·π·fo·C·R2.
The coupling coefficient between the two circuits is
  K  =      M                  L        ⁢                                  ⁢                  1          ·          L                ⁢                                  ⁢        2            where M is the mutual inductance between the two coils. If the two series and parallel circuits are aligned along the axis and there are no power exchanges with the nearby bodies, the power exchanged may be considered equal to Pl=Ps·Q1·Q2·η1·η2·K2 where Ps is the power available to the series resonant circuit of the source device and η1 and η2 are the efficiencies of the two devices, where the first device is the power transmitting circuit and the second device is the power receiving circuit.